Gear transmission mechanisms being the basis of the machine industry have a long history, and it is considered that most of the gear mechanisms were invented before Roman times. In addition, prototypes of screws also date back to Roman times. The gear mechanisms invented in recent years include harmonic drives, which were invented about 40 years ago, or so, and fundamental inventions are virtually non-existent.
Moreover, with regard to bearings, processing techniques for spherical shapes have advanced, and the bearings, which were invented about 80 years ago, are currently in the prime of production and have formed a large industry with a production yield exceeding 50 billion yen in Japan. Thus, rotation mechanisms are of an important and underlying field of social infrastructures, and development and evolution thereof are indispensable for a further social development.
Non-Patent Document 1: “Machine Elements Vol.” authored by Kineo Hayashi, Corona Publishing, published Jul. 1, 1982, pp.117-pp.133
Patent Document 1: Japanese Published Unexamined Patent Application No. 2000-274495